Well-being & psychological distress : genetic and environmental influences on stability, change, and covariance
Appears in the following Collection
- Psykologisk institutt 
AbstractAn important goal to psychological research is to advance knowledge on development and sustenance of positive mental health. This study is the first large scale twin study investigating the genetic and environmental influences on stability and change in both psychological well-being and distress during the developmental juncture of young adulthood. The study also aims to illuminate the extent to which genetic and environmental influences on indicators of well-being and distress are overlapping or distinct. The research material consists of self-report data from a population-based sample of Norwegian twins, born between 1967 and 1979, and measured between the ages of 18 and 31. Structural equation modelling techniques primarily developed for genetically informative data were used in all studies. Positive mental health was conceptualised as either subjective well-being (SWB) or global life satisfaction (LS), whereas psychological distress was conceived of as symptoms of anxiety and depression and self-rated sleep problems.
Recent research into well-being and distress has suggested that emotions are regulated by homeostatic processes designed to maintain emotional set-ranges (Sheldon & Lyubomirsky, 2004) or set-points (Headey, Kelley, & Wearing, 1993). Such set-points refer to the most likely values in a person’s temporal distribution of happiness or unhappiness across the lifespan (Sheldon & Lyubomirsky, 2004), representing some kind of a baseline from which the individual deviates in response to environmental circumstances. A person’s emotional well-being or ill-being is thus hypothesised to oscillate around a “neutral” or average level, with homeostatic forces returning it to its original level after occurrence of pleasant or unpleasant events. Some researchers have suggested that this basal affective level is biologically (Headey & Wearing, 1989) or genetically (Lykken & Tellegen, 1996) determined. Others have underscored the importance of environmental contributions such as early nursing environments and parenting styles (e.g. Bowlby, 1951; Ainsworth, 1962). A vast number of studies have shown that effects from life circumstances and events commonly are short-term, however, with most people displaying an amazing ability for adaptation (e.g. Suh, Diener, & Fujita, 1996).
By suggesting that assumingly beneficial interventions, therapeutic, or societal changes essentially produce transitory effects, such evidence of affective adaptation may be highly discouraging to policy makers and individuals, as well as to the psychological and psychiatric enterprise. When interested in reducing ill-being and improving well-being, questions concerning the reality, rigidity, and nature of affective set-points, is tremendously important. Is there a set-point? How set is this set-point? How is the set-point set? Why do some people remain chronically distressed, whereas others stay mentally healthy? Do early life experiences determine our well-being and ill-being? Are sustainable gains in well-being possible, or is our happiness determined by our unique set of genes?
To address these questions, the first two papers of the present thesis aimed to explore the genetic and environmental risk and protective factors for continuity and change in both well-being and distress in young adults. Paper I explored the magnitude of effects from genes and environment to self-reported SWB, the stability and change in such effects during young adulthood, and sex-specific differences. Paper II investigated the same set of effects for liability to symptoms of anxiety and depression.
The results supported the notion of affective equilibrium levels essentially attributable to a genetic predisposition. For both males and females, considerable stability was found for both well-being and distress, with roughly 80% of the temporal stability being due to additive genetic factors. In contrast, 80% of the time-specific variance was attributable to environmental contributions, indicating that the environment is the main source of change. Thus, levels of well-being and distress were found to change in response to immediate life events, but in most circumstances adapt to an equilibrium, or set-point level. Some new genetic influences emerge, suggesting that the effects of current biological and psychosocial circumstances are of sufficient magnitude to activate different genetic factors over time, and some life circumstances exert long-term effects. Sex differences, both in the set of genes (SWB), and the magnitude of genetic and environmental effects (SWB, psychological distress) were indicated. The major findings from the two longitudinal studies therefore provide strong evidence for the temporal stability of genetic risk factors for SWB and distress in young adults, and substantial sex-specific influences on heritability, stability, and change.
Another important issue in aetiological research on well-being and psychopathology concerns the extent to which risk and protective factors underlying different indicators are common or distinct. Are genetic and environmental determinants of well-being and distress independent or basically overlapping? This question is partly related to the broader and still ongoing debate in psychology concerning the structure of emotions. Many risk and protective factors, both genetic and environmental are not specific to a given phenotype, influencing several correlated phenotypes simultaneously. A second major objective was therefore to further clarify the specificity of the genetic and environmental contributions to the association between well-being and distress.
Using a bivariate model, paper III investigated the extent to which aetiological factors influencing SWB and self-reported sleep problems are distinct or shared. In paper IV this model was extended to explore to what extent the genetic and environmental factors influencing liability to symptoms of anxiety, symptoms of depression, and life satisfaction were overlapping or unique. Two major findings were generated. Firstly, the strong associations between indicators of well-being and distress were to a large extent due to common genetic factors. Secondly, both distinct and overlapping environmental factors were contributing to well-being or ill-being. The results thus indicated substantial overlap in genetic aetiology, for both males and females, and some distinct environmental factors, suggesting that genetic and environmental causes of well-being and ill-being appear to be partly shared, partly distinct.
How may this knowledge be used to improve and promote mental health in individuals and populations? With regard to applied implications, some tentative suggestions and recommendations for future research are presented.
“Happiness and unhappiness are not ends, they are means. They are aspects of mechanisms that influence us to act in the interests of our genes” (Nesse, 2004, p. 1337)
LIST OF PAPERS
Paper I: Nes, R. B., Røysamb, E., Tambs, K., Harris, J. R., & Reichborn-Kjennerud, T. (2006). Subjective well-being: Genetic and environmental contributions to stability and change. Psychological Medicine, 36, 1033-1042.
Paper II: Nes, R. B., Røysamb, E., Reichborn-Kjennerud, T., Harris, J. R., & Tambs, K. (2007). Symptoms of Anxiety and Depression in Young Adults: Genetic and Environmental Influences on Stability and Change. Twin Research and Human Genetics, 10, 450-461.
Paper III: Nes, R. B., Røysamb, E., Reichborn-Kjennerud, T., Tambs, K., & Harris, J. R. (2005). Subjective Well-being and Sleep Problems: A Bivariate Twin Study. Twin Research and Human Genetics, 8, 440-449.
Paper IV: Nes, R. B., Czajkowski, N., Røysamb, E., Reichborn-Kjennerud, T., & Tambs, K. (2006). Well-being and ill-being: Partly different environments, mostly common genes? Submitted.